Piston rings with an electro-chemically applied chrome plated peripheral surface, are known in the art as forming a base for a metallic nitrided face coating. The face coatings complement the hard chrome plate layer by providing advantages not possessed by the said layer, such as strong scuff resistance, extremely high hardness, and low coefficient of friction.
Such metallic nitrided face coatings, however, result in undesirable side effects and limitations, despite the desirable advantages noted above. Because these face coatings may lack strong enough bonds with the underlying substrate, the face coatings can chip so that appropriate coating thickness fails to be achieved. Notwithstanding a suitable substrate, often there is insufficient surface area between the coating and the substrate to promote the necessary bonds. Furthermore, while the wear and scuff resistance of such metallic nitrided face coatings is far superior to chrome plate, current processing methods are unable to produce a layer of sufficient thickness to provide satisfactory wear life in a diesel engine.